USF

Universal Subtitle Format (USF) is/was an ambitious project to standardise a clean, documented, powerful and easy-to-use subtitle file format, written in XML for flexibility, Unicode support, ease of administration and to be hierarchical.

This a subtitle format readable by VLC 0.9.0 and over.

USF is dead, according to this blog post (is this still true? Editors are welcome to edit this page to give more information)